In the next generation of wireless infrastructure (e.g., base stations, backbone, etc.) and customer handsets is called 5th generation mobile networks or 5th generation wireless systems hereinafter referred to as “5G”. 5G is very ambitious and involves millimeter-wave frequency usage, compact phased arrays, and an unprecedented amount of electronic integration. Not only will the transmitters and receivers be integrated into transceivers, but transceivers will be integrated with patch antennas or antenna arrays. The integrated transceiver and antenna or antenna array is referred to hereinafter as an “integrated transceiver-antenna assembly.” In the 5G integrated transceiver-antenna assembly, there will be no traditional connector from the radio electronics to the antenna. For example, the transceiver-antenna assembly may be in the same integrated circuit (IC) package or may be in separate IC packages that are interfaced with one another via, for example, a ball grid array (BGA) interface. In either case, the entire radio, including its antenna or antenna array and its transceiver, will be a single indivisible unit. Therefore, there will be no antenna ports that are accessible from the outside of the unit for connection with an external test system.
Nevertheless, radio manufacturers will want their units tested for all of the usual characteristics, e.g., receiver sensitivity, both without and with interference present, total transmit power, error vector magnitude (EVM) of modulation formats, antenna radiation pattern, etc. All of these parameters must be measured and studied in great detail during the product design phase. In the manufacturing phase, the characterization can be winnowed down, but the speed of testing becomes paramount in order to keep cost down and to be competitive with rival vendors.
The non-separable nature of an integrated transceiver-antenna assembly renders traditional transceiver testing methods useless. Traditionally, one disconnects the antenna and performs all of the receiver and transmitter tests by connecting test equipment to the radio's connector. However, no such connector will be available in the 5G units. Furthermore, the non-separable nature of the 5G integrated transceiver-antenna assembly introduces completely new challenges in testing the antenna itself. Traditional far field test chambers are large and expensive, and therefore manufacturers are eager for compact antenna test solutions, such as near field test systems. However, in order to apply Fourier transform methods to convert near field data to far field radiation patterns, both amplitude and phase information is needed in the near field sampling. When the antenna can be disconnected, this is straightforward to achieve because one can simply use a two-port network analyzer with the antenna of the device under test (DUT) as Port 1 and a calibrated antenna or horn as Port 2. However, when the antenna of the DUT is inseparable from the transceiver of the DUT, phase information can be unreliable because the phase of the local oscillator (LO) of the DUT is likely to drift relative to the phase of the LO of the test equipment.
Also, the speed at which testing is performed is an important issue that is not adequately addressed by any of the known or proposed over-the-air (OTA) test solutions. Many companies have been proposed deploying multiple horns fixed in the far field to try to speed up the measurement of radiation patterns. The problem with such proposals is that, because a far field pattern is a distribution over a sphere and not a plane, the DUT would still need to be gimbaled over azimuth and elevation degrees of freedom rather than over X and Y translation degrees of freedom. If N horns are used to acquire signals simultaneously, a speed-up factor of N can be achieved when scanning a plane or a cylinder, but one encounters frequent redundant azimuth-elevation coordinate access when scanning a sphere. Thus, the speed-up factor is less than N.
Furthermore, with the advent of 5-bit to 6-bit amplitude and phase control of every antenna element in the DUT's patch array, the variety of radiation patterns that a 5G system designer has in his arsenal is huge. Multiplying this by the number of carrier frequencies at which the designer typically wishes to test, and doubling that for both polarizations to be tested, the amount of test data that has to be acquired becomes enormous. In such cases, due to the enormity of the data to be acquired, an entire day may be required to test a single antenna array. Therefore, a large speed-up factor in the amount of time that is required for testing is needed.
Accordingly, a need exists for a test system and method for performing OTA testing of a DUT having an integrated transceiver-antenna assembly that are capable of performing testing in a relatively short amount of time, in a relatively small area and at relatively low cost.